The present invention generally relates to methods and apparatus for registering a plastic fastener tape relative to a web of bag making material in a packaging or bag making machine.
During the automated manufacture of reclosable bags, a continuous length of thermoplastic fastener tape unwound from a supply reel or spool is joined (e.g., by conductive heat sealing) to a continuous web of bag making material (e.g., a monolayer of thermoplastic film or a laminate comprising a first layer of thermoplastic film and a second layer or metal, paper or thermoplastic material). The web-to-fastener tape sealing operation can be performed either intermittently or continuously.
Often the fastener tape has sliders inserted thereon, one slider per section, before that section is joined to the bag making material. In the latter event, it is also customary to form one slider end stop structure per section of the fastener tape prior to the tap being joined to the bag making material. When the fastener tape carries a repeating structural feature (e.g., a slider or slider end stop structure), it is important that that those structural features be accurately placed at regular intervals to ensure their proper registration with respective pockets or receptacles of the packages or bags being manufactured. In particular, each slider end stop structure must be correctly aligned with a corresponding cross seal formed on the package or bag, which cross seal is later divided to become respective side seams of adjacent packages or bags.
Many existing bag making machines produce reclosable bags by a process wherein a continuously advancing folded web of bag making material is incrementally joined to a continuously advancing fastener tape. In subsequent steps, the continuously advancing web/fastener tape assembly is cross sealed to form pockets, the pockets are filled with product and closed, and then the filled pockets are severed from the remainder of the work in process to form completed bags. A drag sealer is a known apparatus for joining a continuously advancing fastener tape to a continuously advancing web of bag making film.
There is a need for a method and an apparatus for inserting sliders and/or forming slider end stop structures on intermittently moved fastener tape at a location upstream of a machine station that joins continuously advancing fastener tape to continuously advancing bag making material.